The present invention relates to nail extractors, and more particularly to a fluid actuated nail extractor employing novel nail engaging jaws, novel actuating and extracting mechanism coupled to the jaws, and a novel pneumatic control system for the actuating and extracting mechanism.
Pneumatic nail extractors in which jaws grip a nail or spike and are pulled from a workpiece by a piston are known in the art. These devices have the advantage of exerting a linear force coaxial with the nail or spike. Because the extraction force is exerted coaxially relative to the nail, the nail is not bent during extraction, thereby preserving the nail as well as reducing the amount of pulling force required.
Where the head of a nail or spike is exposed above the workpiece, one-piece claws as shown in U.S. Pat. No. 2,797,889 to Talboys, or multi-element, spring actuated jaws as shown in U.S. Pat. No. 2,945,674 to Hursh, are feasible. Where, however, a nail head does not extend above the workpiece surface, a strong clamping action of the claws is required in order to penetrate the workpiece surface and clamp the nail. U.S. Pat. Nos. 2,570,914 to Buck, 2,709,570 to Henry, and 2,735,649 to Swallert show pneumatic nail extractors in which jaw mechanisms or jaw actuators are driven downwardly by pneumatic pistons to provide a strong clamping action to penetrate the workpiece surface. Such extractors, however, exhibit a distinct disadvantage because the strong downward action of the piston exerts a reactive force on the piston and cylinder that can cause the entire extracting tool to jump from its centered position over the nail. If this occurs, the extracting tool will not be properly positioned when the jaws are driven closed, thereby destroying the nail head or missing it entirely. Other nail extractors are known in which upward movement of pneumatic pistons cause clamping of jaws as well as upward movement of the jaws. Examples of such devices are found in U.S. Pat. Nos. 1,771,712 to Jimerson and 2,846,187 to Sublett et al. Such devices are adequate where the head of a nail or spike is above a workpiece. However, in order to prevent the jaw mechanism from rising before it is clamped about a nail, the initial piston action must be retarded in some manner, while a quick clamping action is required in order to penetrate a workpiece surface to extract a nail.
It is a broad object of the present invention to provide a pneumatically powered nail extractor that overcomes the problems discussed above. Further objects of the present invention are to provide a nail extractor that has a rapid nail clamping action while exerting a very small, if any, reactive force on the extractor that may cause the extractor to become misaligned with a nail to be pulled; to provide a relatively lightweight nail extractor that sequentially clamps the nail and thereafter extracts it with minimum effort required by the operator of the extractor; to provide a pneumatically powered extractor having a minimum number of moving parts that resets itself after each extraction cycle; to provide a nail extractor that requires a minimum maintenance effort and is relatively inexpensive to manufacture; and to provide a safety mechanism on the extractor that will normally prevent its operation when not aligned with a nail to be extracted from a workpiece.